Microelectronic elements such as semiconductor chips are commonly provided in packages having terminals connected to the microelectronic element itself, such terminals being available for connection to external elements such as printed circuit boards.
Some microelectronic elements, notably memory chips, have been provided heretofore in stacked arrangements with packages superposed one atop the other to conserve space on a circuit board. Such structures typically involve only a few chips and relatively simple connections which normally do not involve interconnections between chips in the stack, or between multiple stacks of chips. Even in these situations, it is sometimes necessary to provide different packages for different chips in the stack.